title: βIV-Spectrin and CaMKII facilitate Kir6.2 regulation in pancreatic beta cells.
abstract: Identified over a dozen years ago in the brain and pancreatic islet, βIV-spectrin is critical for the local organization of protein complexes throughout the nervous system. βIV-Spectrin targets ion channels and adapter proteins to axon initial segments and nodes of Ranvier in neurons, and βIV-spectrin dysfunction underlies ataxia and early death in mice. Despite advances in βIV-spectrin research in the nervous system, its role in pancreatic islet biology is unknown. Here, we report that βIV-spectrin serves as a multifunctional structural and signaling platform in the pancreatic islet. We report that βIV-spectrin directly associates with and targets the calcium/calmodulin-dependent protein kinase II (CaMKII) in pancreatic islets. In parallel, βIV-spectrin targets ankyrin-B and the ATP-sensitive potassium channel. Consistent with these findings, βIV-spectrin mutant mice lacking CaMKII- or ankyrin-binding motifs display selective loss of expression and targeting of key protein components, including CaMKIIδ. βIV-Spectrin-targeted CaMKII directly phosphorylates the inwardly-rectifying potassium channel, Kir6.2 (alpha subunit of KATP channel complex), and we identify the specific residue, Kir6.2 T224, responsible for CaMKII-dependent regulation of KATP channel function. CaMKII-dependent phosphorylation alters channel regulation resulting in KATP channel inhibition, a cellular phenotype consistent with aberrant insulin regulation. Finally, we demonstrate aberrant KATP channel phosphorylation in βIV-spectrin mutant mice. In summary, our findings establish a broader role for βIV-spectrin in regulation of cell membrane excitability in the pancreatic islet, define the pathway for CaMKII local control in pancreatic beta cells, and identify the mechanism for CaMKII-dependent regulation of KATP channels.
authors.affiliation: Dorothy M. Davis Heart and Lung Research Institute, Department of Molecular and Cellular Biochemistry, Division of Cardiovascular Medicine, Department of Internal Medicine, and Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH 43210.
authors.forename: Crystal F
authors.initials: CF
authors.lastname: Kline
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Wright
authors.forename: Olha M
authors.initials: OM
authors.lastname: Koval
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Zmuda
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Johnson
authors.forename: Mark E
authors.initials: ME
authors.lastname: Anderson
authors.forename: Tsonwin
authors.initials: T
authors.lastname: Hai
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Hund
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Mohler
mesh_terms: D000818:Animals; D017487:Ankyrins / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D015151:Immunoblotting; D007150:Immunohistochemistry; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000235:genetics / Q000502:physiology; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D009154:Mutation; D010766:Phosphorylation; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D011485:Protein Binding; D013049:Spectrin / Q000235:genetics / Q000378:metabolism*; D000099161:Kcnj11 Channel
chemical_list: D017487:Ankyrins; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D024661:Potassium Channels, Inwardly Rectifying; D013049:Spectrin; D000099161:Kcnj11 Channel; C498995:Ank2 protein, mouse; C504042:betaIV spectrin, mouse
keywords: local regulation; trafficking